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PRODUCT SPECIFICATION
RC4190
17
Troubleshooting Chart
Symptom
Draws excessive supply current on start-up
Possible Problem
Battery not "stiff" — inadequate supply bypass capacitor.
Inductance value too low.
Operating frequency (F
O
) too low.
Inductance value too high for F
O
or core saturating.
Not potted well or bolted loosely.
Normal operating condition.
Inductor is saturating:
1. Core too small.
2. Core too hot.
3. Operating frequency too low.
Output voltage is low.
Inductor "sings" with audible hum.
L
X
in appears noisy — scope will not synchronize.
Inductor current shows nonlinear waveform.
Inductor current shows nonlinear waveform.
Waveform has resistive component:
1. Wire size too small.
2. Power transistor lacks base drive.
3. Components not rated high enough.
4. Battery has high series resistance.
Inductor current is linear until high current is
reached.
External transistor lacks base drive or beta is too low.
Poor efficiency.
Core saturating.
Diode or transistor:
1. Not fast enough.
2. Not rated for current level (high V
CE
SAT).
High series resistance.
Operating frequency too high.
Loop stability problem — needs feedback capacitor from
V
OUT
to V
FB
(pin 7), 100 to 1000 pF.
Motorboating (erratic current pulses).
65-3464-04
I
LX
-I
MAX
Time
65-3464-05
I
LX
-I
MAX
Time
65-3464-06
I
LX
-I
MAX
Time